The role of antibodies in control or prevention of HIV infection is controversial. Humans infected with HIV do mount antibody responses following infection, including virus- neutralizing responses, but those responses are not adequate to contain or prevent infection. Infection induces relatively poor quality neutralizing Ab responses of modest titer, in most cases. One of the central obstacles that make it difficult to contain virus on a chronic basis obviously is viral variation, which rapidly accomplishes escape from binding and neutralization. However, during acute infection it is less clear why effective antibody responses are not induced. We believe that HIV infection causes dysregulation of T cell help that is required for elaboration of high quality antibodies. If this hypothesis is true, then there is some hope that induction of antibodies by exposure to neutralizing determinants during good viral control in healthy infected long term nonprogressors or controllers (in a context where CD4+ T cell dysfunction is not present) might induce protective antibodies that are not possible to induce during infection. In the work proposed in this application, we will explore the molecular and genetic basis for elaboration of highly functional HIV-specific antibodies. The basic approach involves sorting and cloning single HIV-specific B cells from LTNPs or normal progressors, and comparing the repertoires. We will express recombinant human antibodies derived from single cells, and test the function of these antibodies. The studies will yield fundamental new knowledge about the antibodies that are associated with broad and effective neutralizing activity. This collaborative group, combining the expertise of a human B cell immunology laboratory and an HIV biology laboratory, will explore the molecular and genetic determinants of highly functional antibodies against HIV. The proposed work uses state- of-the-art technology to isolate single B cells from infected subjects, long term nonprogressors and other infected individuals, and then to clone the antibody genes from the single cells. The genetic features of the HIV-specific antibodies will be defined, and recombinant human monoclonal antibodies specified by these genes will be made for study of how broadly neutralizing HIV antibodies function. [unreadable] [unreadable] [unreadable]